The present invention relates to treatment of cancer, and more particularly to a cancer treatment system delivering thermal energy from a body cavity to a cancerous volume of tissue while supplementing the effects of the thermal therapy with a complementary treatment mechanism introduced into the cancerous volume of tissue.
Many devices have been proposed for intracavitary treatment of diseased tissue. One of the most successful devices is disclosed in U.S. Pat. No. 5,330,518 entitled METHOD FOR TREATING INTERSTITIAL TISSUE ASSOCIATED WITH MICROWAVE THERMAL THERAPY, which is hereby incorporated by reference. The disclosed device is inserted into a bodily conduit, such as a urethra, for treating a target volume of tissue, such as a prostate. The device includes a microwave antenna and a cooling system, so that the target volume can be heated to a temperature greater than about 45.degree. C. while maintaining the bodily conduit at a safe temperature. The device may be operated to necrose the target volume of diseased tissue while preserving adjacent healthy tissue and the healthy tissue of the bodily conduit. The intracavitary nature of the device with cooling of the urethra minimizes the trauma associated with the treatment by avoiding puncturing or removing the urethra which occur with surgery and other more invasive procedures. This also minimizes the requirement for anesthesia during the procedure, the post-treatment discomfort such as dysuria and long term morbidity effects such as incontinence or impotence which are associated with more invasive procedures such as surgery and interstitial therapies.
In some situations, a cancerous volume of tissue is located a distance from the bodily conduit that makes it quite difficult to heat the diseased tissue to a sufficient temperature for a sufficient period of time to necrose the diseased tissue without harming intervening healthy tissue, particularly the wall of the bodily conduit. For example, when the prostate is afflicted with cancer, prostate tissue located near the periphery of the prostate, known as the prostatic capsule, is often among the tissue that is cancerous. The distance from the urethra to the outside of the prostatic capsule is so large as to present significant hurdles to thermally treating the cancerous tissue to cause necrosis while preserving the urethral wall and controlling the temperature at the rectum, which is susceptible to thermal damage.
Another method of treating cancerous tissue involves interstitial implantation of heat-emitting or radiation-emitting seeds. For example, a plurality of seeds may be implanted within prostate tissue through the perineum to treat prostate cancer. While this method is effective to deliver a sufficient dose of thermal energy or radiation to the target volume of diseased tissue, it is highly invasive and significant irritating symptoms and voiding dysfunction often occur following seed therapy as a result of both the multiple transperineal punctures required to insert the seeds and the effect of radiation over time. The long term effects of interstitial seed implantation are only known in patients with relatively low grade cancers, and even these results appear to be less effective than traditional surgery. A likely explanation for the lesser success of seed therapy is that it is difficult to precisely locate the position and extent of cancer in the prostate, and since the entire prostate is not removed as with surgery, there is a possibility that the radiation from the seed may leave some cancerous portions of the prostate untreated. There is even some data indicating that recurrent cancers that are not fully treated are more serious and faster growing than the original cancers. Therefore, interstitial seed therapy alone does not present an optimal treatment alternative for prostate cancer.